ASUNCIÓN, PARAGUAY—“Change or death.” That’s the stark campaign slogan of Fernando Lugo in his bid to become Paraguay’s next president.

The outspoken populist appeals to the poor—but he also increasingly resembles Latin America’s leading anti-democratic firebrand, Venezuelan president Hugo Chávez.

His candidacy is cause for concern that Paraguay’s gradual 18-year move toward democracy may be reversed. The last thing Latin America needs is another populist troublemaker.

Already, Paraguay’s democratic progress has taken a few hits under the current government. President Nicanor Duarte Frutos, whose term ends next August, has tried—unsuccessfully so far—to amend the Constitution so he can run for reelection. As his campaign to remain in control becomes more desperate, so have his methods. They have grown increasingly strident and confrontational—common in a region long known for populist politics.

His party, the traditional National Republican Association, or Colorado Party as it is known, has split into three factions, with little likelihood of reconciliation.

That means the opposition is now poised to assume power. As bad as Mr. Duarte may seem, the opposition is worse; as is its leading candidate, Mr. Lugo.

A former priest who became bishop of San Pedro, Lugo has long been involved in politics and is known as an outspoken advocate of a controversial ideology popular in the 1970s and 1980s known as liberation theology. This earned Lugo the title of Paraguay’s “Red Bishop.”

The Catholic Church hierarchy dismissed Lugo from his clerical duties when he announced his candidacy for president, but that didn’t stop him. On the contrary, his removal from the clergy appears to have intensified his anti-democratic stances, which increasingly allies Lugo with Venezuela’s Mr. Chávez and Bolivia’s Evo Morales. On a billboard that rises over Asunción’s main boulevard, for example, the Lugo campaign advertises the slogan, “Change or death,” and brags that their candidate doesn’t consider himself “a slave of the law.” So much for the rule of law.

The opposition faces a dilemma. If it continues to support Lugo, it could win—maybe—but will have to deal with a demagogue who thumbs his nose at the law and could plunge the country into chaos. If it enters the elections divided—already, three parties have split off from the original coalition of 10—and offers several candidates, it is almost sure to lose. Worse, Lugo could go all the way and become a dictatorial strongman like Chávez.

Though the political class is wary of him, Lugo has broad support among the country’s poor, who are drawn to his populist rhetoric about the evil rich and the need to redistribute wealth to those less fortunate.

Ranting about the rich has broad appeal because Paraguay is a poor country with a high unemployment rate—nearly half the labor force works in agriculture, more than 16 percent of the population is unemployed, and 36 percent of all Paraguayans live below the official poverty line. And while not totally in shambles, its economy is languid, growing at a compounded annual rate of just 1.3 percent per year over the past five years, according to The Heritage Foundation and The Wall Street Journal’s 2007 Index of Economic Freedom, which ranks the economy well down the list in terms of openness—99th out of 157 globally, and 22nd out of 29 in the Americas.

With a weak economy; high levels of government corruption; and a restrictive, highly regulated, labor market—one of the worst in the world—Paraguayan society is ripe for the kind of politics-of-envy message being peddled by Lugo. This is all music to Chávez’s ears.

For now, the likely outcome is far from clear. Lugo’s words and actions have created considerable unease among many even within his own coalition. The ruling party is torn by divisions. There are even proposals afoot to legally block Lugo’s candidacy.

The unease is also spreading to neighboring countries, especially Brazil, which are understandably concerned about having another radical populist in the neighborhood.

Meanwhile, the clock is ticking—not only for Paraguay, but for all of Latin America, which hardly needs another populist strongman to add to the region’s problems.